Aircraft development is a capital-intensive and usually lengthy process. Further, because the viability of aircraft depends largely on their weight, conservatism in design can have powerful consequences on the viability of an aircraft. As a result of these two factors and other considerations, any given aircraft tends to be specialized for one role or mission during the design process.
At the same time, aircraft are used on and needed for a variety of missions and roles. Aircraft carry different payloads, including for example, passengers, cargo, sensors, and munitions. Beyond payload, other requirements can shape an aircraft design; for example, some missions require flight in a certain speed regime, while other missions require high fuel efficiency.
Prior art approaches to providing aircraft suitable for conducting specific missions tend to either (i) design a distinct aircraft for a specific mission, (ii) adapt an existing aircraft design for another mission through modifications (iii) attempt to bridge multiple missions in the design stage through an a priori requirement.
Each of these three prior art approaches has weaknesses. The first approach, to design a distinct aircraft for a specific mission, is extremely expensive and often impractical. In general, it has the least potential to meet multiple diverse requirements, therefore limiting its market. The second approach, post-hoc adaptation, is often used in adapting aircraft to new missions similar to the original design mission. Even this approach is expensive and time consuming, however. These difficulties arise in part because of formidable certification and qualification requirements. An example of aircraft post-hoc modification is the transformation of the Lockheed L-188 Electra civilian passenger transport into the Lockheed P-3 Orion naval maritime surveillance aircraft. The original mission (passenger transport) and the new mission (maritime surveillance) have similar flight envelope requirements, in terms of speed and altitude.
The third general approach, attempting bridge multiple missions in the design stage through an a priori requirement, often entails extraordinary costs and engineering effort. An example of this approach would be the Lockheed Martin F-35 family of supersonic fighter aircraft, attempting commonality between the F-35B short takeoff and vertical landing (STOVL) platform, the F-35C carrier based fighter platform, and the F-35A land-based conventional takeoff supersonic fighter platform. The F-35 program is renowned for being billions of dollars over budget and years behind schedule; this results at least in part from attempts to achieve high degrees of commonality among the aircraft in the family. The Boeing competitor to the F-35, as described in U.S. Pat. No. 5,897,078 struggled with similar issues in attempting to bridge diverse mission requirements, while still retaining some degree of parts-commonality among variants.
The '078 patent and all other extrinsic materials discussed herein are incorporated by reference in their entirety. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.
In summary, aircraft are sometimes designed to be flexible, yet this by-design flexibility can only go so far. Alternatively, different versions of aircraft are designed for specific needs, users, and missions. Only a few prior art aircraft and aircraft related developments known to the inventor have had elements of modularity, and no known prior art aircraft have achieved complete or even extensive modularity.
A few cargo aircraft have carried their cargo in removable cargo containers. Notably, the Fairchild XC-120 Packplane, Miles M.68 Boxcar, and Kamov KA-226 are the instances known to the inventor. FIG. 1A illustrates the Kamov KA-226 helicopter 110, which features a main portion 112 of the aircraft and a removable cargo container 114, which can be configured to carry passengers. FIG. 1B is a side view illustration of the Miles M.68 Boxcar 120, which is a fixed-wing transport aircraft having a main portion 114 of the aircraft, and configured to carry cargo in a removable cargo container 124.
While these prior art aircraft carry their cargo payload in removable containers, they cannot be said to be truly modular aircraft, because they do not change containers to change missions or roles. These prior art aircraft are really predominantly single-role transport aircraft that happen to carry their cargo in an external container that forms part of the aerodynamic fairing of the aircraft, rather than carrying their cargo in containers internal to the aerodynamic fairing of the aircraft like most air freighters.
Aircraft designed to have large cargo bays also do not lend themselves to modularity because the wings need to have structural support across the fuselage. Such structural supports are either positioned above the fuselage (in a high wing configuration) or below the fuselage (in a low wing configuration). In either of those configurations it is not practical to provide readily replaceable wings.
In a similar vein, but for a different kind of aircraft, U.S. Pat. No. 4,736,910 to O'Quinn is directed to a light fighter aircraft with interchangeable nose and tail sections. U.S. Pat. No. 3,640,492 is directed to aircraft having electronics or avionics equipment in removable portions of the aircraft structure or aerodynamic fairing. U.S. Pat. No. 7,234,667 to Talmage describes the division of an aircraft into sections, any of which could be recovered by parachute following an in-flight incident. U.S. Pat. No. 6,098,927 describes an aircraft with a removable fuselage section to increase or decrease the payload capacity of the aircraft. Related to this idea, the practice of extending or contracting fuselage sections by the addition or removal of fuselage plugs is known in the art, and is commonplace in stretched families of transports, including for example, the Airbus A318, A319, A320, and A321, which are substantially just stretched versions of the same aircraft accommodating 107-220 passengers. Unless the context dictates the contrary, all ranges set forth herein should be interpreted as being inclusive of their endpoints, and open-ended ranges should be interpreted to include only commercially practical values. Similarly, all lists of values should be considered as inclusive of intermediate values unless the context indicates the contrary.
US Patent Application 2008/0017426 describes a somewhat modular ground vehicle, wherein a core vehicle can attach to a variety of interchangeable elements to serve different roles or missions. However, it should be noted that the field of ground vehicles is substantially different from the field of aircraft, and that aircraft are subject to stricter design constraints. For example, aircraft are highly weight sensitive and aerodynamic drag sensitive and poorly tolerate structural and powerplant inefficiencies, such as those built into the ground vehicle of 2008/0017426 for modularity. A person of ordinary skill in the art would not expect systems and methods that work on ground vehicles to also work on aircraft without significant additional inventive subject matter.
It should be noted that a key constraint for adapting aircraft to serve different roles and missions is the operator interface. As an example, consider the vastly different pilot interfaces found among helicopters, transport aircraft, fighter aircraft, and the ground stations of unmanned aircraft. If an aircraft is to serve multiple roles and missions, it must have a suitable and adaptable interface. This is a formidable challenge, and relatively little known prior art addresses this challenge.
U.S. Pat. No. 5,626,030 to Watson describes a ground-based flight simulator that uses parts of an actual aircraft. However, this reference does not provide a ground control station for an aircraft that is common to a cockpit of an aircraft. U.S. Pat. No. 5,880,669 to Romanoff, et al. also describes an aircraft simulator system, but does not disclose a ground control station for an unmanned aircraft that is substantially identical to a cockpit for a manned aircraft.
Thus, there is still a need for aircraft that are quickly and economically adaptable to different roles and missions, not simply adaptable to different payloads—aircraft that are both modular and multirole.